Climate change impacts on rainfed agriculture and mitigation strategies for sustainable agricultural management: A case study of Prince Edward Island, Canada

Abstract

AbstractRainfed agriculture in Prince Edward Island is affected by climatic changes like warming, seasonal shifts, varying precipitations, and reducing water availabilities, all questioning its sustainability. Projecting future scenarios was critically important; therefore, spatiotemporal variations in potential evapotranspiration (PET), crop water requirements (CWRs), effective rainfall (ER), supplemental irrigation requirements (SIR), and sustainable water availabilities (SWAs) were analyzed. Average annual PET was predicted to insignificantly increase (3% to 6%) under RCP4.5 during the next 30–60 years, with two to four times increase in colder months (January–April) and a significant reduction during August–December. Accordingly, historical CWR of potatoes (currently ~425 mm) would decrease by 5% to 9%, except for the least likely RCP8.5 scenario, which projects ~10% increase in 2051–2080. That, and changes in ER, would cause SIR to decrease to 50–90 mm in normal years, but two to three times higher during dry years, and almost no SIR in wet years. Spatially, SIR increases by ~40 mm from east to west and is expected to be higher in 2021–2050 than 2051–2080. Monthly SIR ranges in normal years would be July: 02–36 mm, August: 31–48 mm, and September 04–20 mm. Existing water policy allows pumping up to 20% of yearly recharges (annual SWA) and up to 35% of summer's streams baseflows (summer SWA). Despite insignificant reductions in annual SWA (3% to 17%) for the next 30–60 years, summer SWA may be reduced 38% to 50% due to temporal redistribution. Even in dry years, the reduced amounts would still be sufficient to fulfill SIR in the eastern forest‐dominated Bear River watershed and SIR in normal years in the central zone; however, they would not be enough to enable the entire cultivated area of western zone. In normal years, SIR would consume: 5% to 6%, 27% to 37%, and 63% to 79% of annual SWA in the eastern, central, and western zones, respectively. Sprinkler irrigation to meet SIR is challenging, more economic evaluations and policy adaptations are needed for sustainable agricultural management.